This invention pertains to a control valve providing rapid advance, slow metered advance, hold and return action for a single-acting cylinder wherein all of the operations are under the control of a single handle connected to a rotatable valve member and wherein there is no pressure loss in the motor when the valve is shifted between rapid advance, metered advance and hold positions (non-interflow).
Three-position rotary control valves providing for plural operations of a motor are well known in the art, as seen in McClocklin U.S. Pat. Nos. 3,892,259 and Re. 30,517.
A rotary directional control valve having a valve member which coacts with four ports is shown in Schultz U.S. Pat. No. 3,677,295.
In certain types of test equipment, the normal testing cycle requires conventional advance, return and hold operations of a linear motor as well as a slow metered advance, with a carefully controlled rate of movement of the motor being controlled by the valve. A prior art commercial control used in such equipment has a flow control valve unit generally of the type shown in Swanson U.S. Pat. No. 3,217,731 wherein a handle associated with the flow control valve unit can be positoned to provide for either rapid advance or metered advance of the motor. In the commercial control, a second valve structure operable by a second handle is added into the hydraulic circuit and the second handle is positioned to provide for either advance operation, hold operation or return operation. It is not possible to obtain all of the four desired modes of operation by control of four valve positions by a single handle.